In recent years, a wireless power transmission technology has been paid attention as technologies for supplementing shortage of battery capacity in accordance with an increase in the power consumption due to improvements in the performances of functions and diversification of contents while a variety of mobile equipment inclusive of portable telephone has been widely used.
The wireless power transmission technology is required to have an ability to stably feed a variety of loads with power, or no-load dependency since neither the power consumption of the mobile equipment nor the load in each state of charge of the battery is constant upon transmitting electric power in a non-contact manner.
A non-contact power feed apparatus of such a configuration that the power transmitting antenna and the resonance capacitor on the power transmitting side are connected in series, and the power receiving antenna and the resonance capacitor on the receiving side are connected in parallel is disclosed as a wireless power transmission technology having such no-load dependency. The non-contact power feed apparatus can be operated as an ideal transformer depending on how to take the capacitance values of the resonance capacitors on the transmitting and receiving sides (See, for example, a Patent Document 1).